This invention relates to an ultrasonic probe which is used for an ultrasonic medical diagnostic apparatus and which serves as a transmitter and receiver of a sound wave.
There are various types of ultrasonic diagnostic apparatus, and hence, various types of ultrasonic probes for various purposes.
As representative ultrasonic probes, there are a single-type ultrasonic probe which essentially consists of a sheet of circular piezoelectric vibrator and an array-type ultrasonic probe in which multiple strips of micro piezoelectric vibrators are arrayed on a straight line. Since the structures of these probes are basically the same, the array-type ultrasonic probe will be explained as an example in the following.
The array-type ultrasonic probe is composed of multiplicity of strips of piezoelectric vibrators with electrodes attached onto both surfaces. Piezoelectric ceramic or the like is used for the piezoelectric vibrator and those piezoelectric vibrators with electrodes are set in array. On the electrode of the piezoelectric vibrator on the side of an object to be examined an acoustic matching layer is formed and, if necessary, an acoustic lens is disposed thereon. On the other hand, on the surface of the piezoelectric vibrator contrary to the object to be examined a backing load member is provided.
The acoustic matching layer consists of one or two layers made of glass, plastic material which is mixed with tungsten powder, or epoxy resin. When the acoustic matching layer made of these materials is attached to the piezoelectric vibrator, an adhesive should be made even and thin, and when the ultrasonic probe is operated with high-frequency waves, the matching layer should be made very thin to a degree of the order of several tens of microns, which makes the manufacture of the ultrasonic probe very difficult.